Notes on Immunology, Immunodeficiency, and Autoimmunity

Introduction to Immunology
- Innate Immunity: First line of defense, includes barriers like skin and mucous membranes.
- Adaptive Immunity: Specific responses involving lymphocytes (B and T cells).

Effector Cells:
- Innate Cells:
- Dendritic Cells: Phagocytize antigens and present them to T cells.
- Macrophages and Neutrophils: Involved in phagocytosis and inflammatory responses.
- Adaptive Cells:
- B Cells: Produce antibodies.
- T Cells: Require MHC for activation.
Key Cytokines:
- IL-10, IL-12, TNF-α, IFN-γ: Regulate immune responses, inflammation.

Immunodeficiency:
- Characterized by reduced or absent immune response, leading to infections.
- Primary vs. Secondary Immunodeficiencies:
- Primary: Genetic
- Secondary: Environmental factors (e.g., cancer treatment, HIV, or infections).
Autoimmunity:
- Occurs when the immune system mistakenly targets self-antigens, leading to tissue damage.
- Can affect specific organs or be systemic (e.g., RA, SLE).

Triggers of Autoimmunity:
- Failing self-tolerance: Genetic predispositions, environmental triggers, molecular mimicry.
- Types of autoantibodies: can cause direct damage to tissues, e.g., anti-DNA, anti-TPO, rheumatoid factors.
T Cell Involvement:
- Activation can lead to proliferation or tolerance based on how antigens are presented.
- TCR-mediated recognition of self versus foreign antigens is critical for maintaining self-tolerance.

B Cell Tolerance Mechanisms:
- Negative selection and receptor editing in the bone marrow.
- Production of autoantibodies can initiate or exacerbate autoimmune processes.
Cytokines involved:
- BAFF (B-cell activating factor): Regulates B cell survival; altered levels correlated with autoimmunity.

Molecular Mimicry:
- Pathogens present on antigens resembling self-antigens, e.g., Streptococcus and rheumatic fever.
Bystander Activation:
- Non-specific lymphocyte activation in a pro-inflammatory environment may lead to autoimmune responses.
Epitope Spreading:
- Exposure of cryptic self-antigens following tissue damage can lead to widespread autoimmune reactions.

Immunosuppression:
- Use of corticosteroids, biologics (e.g., TNF inhibitors, anti-CD20 agents) to reduce immune activity.
Personalized Immunotherapy:
- Tailoring treatment based on individual's immune characteristics, though risks include rejection.
Supportive Care:
- Nutritional support, managing infections, like using anti-inflammatories and immune replacement therapies.

Type I Diabetes Mellitus: Autoantibodies target pancreatic beta cells, leading to insulin deficiency.
Multiple Sclerosis: Immune-mediated attack on the myelin sheath of nerves, leading to neurological deficits.
Rheumatoid Arthritis: Autoantibodies formed against cartilage leading to joint inflammation.
Systemic Lupus Erythematosus (SLE): Multi-system disorder characterized by diverse autoantibodies and damage to tissues.

Clinical Features:
- Recurrent infections, failure to thrive, unusual infections.
Primary Immunodeficiencies:
- Severe Combined Immunodeficiency (SCID), X-linked Agammaglobulinemia (Bruton’s), DiGeorge Syndrome.
Secondary Immunodeficiencies:
- Acquired infections (e.g., HIV), cancers, treatments that suppress immune response.

HIV Pathogenesis:
- HIV infects CD4+ T lymphocytes, leading to immune collapse and increased susceptibility to infections and برخی cancers.
Treatment:
- Antiretroviral therapy to manage viral load, HAART regimens that include NRTIs, NNRTIs, PIs, and INSTIs.
Prevention Strategies:
- PrEP and PEP for at-risk populations, emphasizing early diagnosis and treatment adherence.